The present invention relates to tension-operated line release systems and in particular to parachute harness load releasing systems.
In an aircraft escape system, the crewman, his body armor, parachute and survival equipment are pulled clear of the aircraft by a rocket which is launched ahead of the crewman by an explosive cartridge powered catapult. The rocket is attached to the crewman's parachute harness by a nylon line pendant, which is subjected to varying tension loads depending on whether, and how long ago, the rocket has been launched, ignited, or burned out. Following launch of the rocket, the pendant line pays out at a very low tension until it reaches full extension, when rocket ignition is triggered. Following ignition, rocket thrust and pendant line tension increases rapidly to a maximum, remains substantially constant thereafter for approximately 90% of burn time, then falls to zero during a trail out period. After the crewman has been pulled clear of the aircraft, he can be carried some distance away from the aircraft and his parachute can be deployed. It is necessary to detach the rocket and pendant line from the crewman shortly before rocket burnout in order to prevent their possible entanglement with the shroud lines or canopy of the opening parachute. It has been the general practice to actuate the pendant release latch used in this system with an explosive cartridge contained in a case attached to the crewman's parachute harness and connected to the pendant line release latch by flexible tubing. The cartridge is fired, via a time delay fuse, by a detonator fired when the crewman leaves the seat. While this device has served the purpose, it has not proven entirely satisfactory because it does not always release the pendant line at the right point in the rocket burn period due to variation in the required time interval with flight conditions, rocket impulse, and launch velocity, and due to variation in fuse time due to manufacturing tolerances. In addition, hardware containing an explosive charge must be carried on the user's harness or vest, thereby adding weight, increasing bulk, and creating an additional hazard to the user by its very nature.